The spinning machines to which this invention relates are preferably of the type known as "ring spinning machines", however, the invention can be used to advantage on other long spinning machines that have drawing frames, such as cannister spinning machines, flyers or the like, that have several lower rollers.
Rotatably supported upper rollers are pressed onto the driven lower rollers of the drawing frame of such spinning machines, and by means of the varying circumferential speeds of the lower rollers fiber strands supplied thereto and which are squeezed between the upper and lower rollers are drawn therethrough. The lower rollers of the drawing frame which are arranged lengthwise of the machine are formed by very long roller lines, which extend along all of the drawing frames. It is common practice to drive the roller lines that form the output lower rollers of this drawing frame at both of its ends by a motor, and further to drive the other roller lines on the machine by means of this roller line by step-down gear transmissions at stepped-down, lower rpm's. The ends of these roller lines opposite the drive side thereof have ended up free in the conventional spinning machines i.e., they have never been driven at each end. Because of the great length of the roller lines it is thus impossible to prevent them from twisting during operation, with the torsion on the free ends of the rollers being caused to increase from one line to the next and consequently being the greatest at the last drawing frame. The torsion of the roller lines is caused by the drive power which is transferred by these lines to the upper rollers, and by the friction in the numerous roller line supports.
The torsion in the roller lines causes draw malfunctions and has therefore disadvantageous effects on the quality of the produced yarns or unfinished yarns. Such torsion can lead to torsion variations in the bottom roller lines and as a consequence the uniform operation of the drawing process is prevented and periodic thickness variations of the yarn or unfinished yarn can thus result, from such machine operation which in extreme cases can lead to unusable yarns or unfinished yarns. The resulting average values of the torsion in the roller lines during operation of the machine regardless of whether they are overlapped by torsion variations or not, can be extremely disadvantageous, especially in connection with periodic idleness of the machine, which is necessary occasionally to exchange the empty spools or cartridges. Th torsions present during operation of the machine decay when the machine is idle and can thereby cause draw malfunctions and naturally this will lead to thread breaks when the machine is again started. Thus the next-to-last roller line in the thread supply feeding device of a drawing frame has a higher torsion than the roller line which forms the lower supply roller located on the output side of the drawing frame, which can lead to a temporary interruption of the thread feed to the supply roller pairs and thereby ultimately to thread breaks.
The drawing malfunctions caused by torsion and/or torsion fluctuations of the roller lines have been solved in the past by limiting the length of the spinning machine and by using roller lines of the greatest possible diameter. The diameter of the roller lines depends, however, on technical spinning factors, and one cannot enlarge them too much for reasons of space. It is also desirable in many cases to diminish the diameter of the roller lines, in order to be able to spin fiber strands with a shorter stacking length, which accordingly require a smaller field of distortion, without having to have a shorter spinning machine for this purpose. It would be much more desirable, on the other hand, to be able to lengthen the spinning machine, since the economy of a spinning machine increases with the increased number of its drawing frames.